Unit 2 – The Cell n Chapter 7~ A Tour of the Cell

Cytology: science/study of cells n Light microscopyresolving power~ measure of clarity n Electron microscopy TEM~ electron beam to study cell ultrastructure SEM~ electron beam to study cell surfaces n Cell fractionation~ cell separation; organelle study n Ultracentrifuges~ cell fractionation; 130,000 rpm

Cell Types: Prokaryotic n Nucleoid: DNA concentration n No organelles with membranes n Ribosomes: protein synthesis n Plasma membrane (all cells); semi-permeable n Cytoplasm/cytosol (all cells)

Cell size n As cell size increases, the surface area to volume ratio decreases n Rates of chemical exchange may then be inadequate for cell size n Cell size, therefore, remains small

Nucleus n Genetic material... chromatin chromosomesnucleolus: rRNA; ribosome synthesis n Double membrane envelope with pores n Protein synthesis (mRNA)

Ribosomes n Protein manufacture n Free cytosol; protein function in cell n Bound endoplasmic reticulum; membranes, organelles, and export

Endomembrane system, I n Endoplasmic reticulum (ER) n Continuous with nuclear envelope n Smooth ER no ribosomes; synthesis of lipids, metabolism of carbohydrates; detoxification of drugs and poisons n Rough ER with ribosomes; synthesis of secretory proteins (glycoproteins), membrane production

Endomembrane system, II n Golgi apparatusER products are modified, stored, and then shipped n Cisternae: flattened membranous sacs n trans face (shipping) & cis face (receiving) n Transport vesicles

Endomembrane system, III n Lysosomes sac of hydrolytic enzymes; digestion of macromolecules n Phagocytosis n Autophagy: recycle cell’s own organic material n Tay-Sachs disease~ lipid-digestion disorder

Endomembrane system, IV n Vacuoles membrane-bound sacs (larger than vesicles) n Food (phagocytosis) n Contractile (pump excess water) n Central (storage in plants) tonoplast membrane